Background: Early-onset cancer (diagnosed under age 50) generally manifests as an aggressive disease phenotype. The association between healthy lifestyle and early-onset cancer and whether it varies by common genetic variants remains unclear.
Methods: We analyzed a prospective cohort of 66,308 participants who were under age 50 and free of cancer at baseline in the UK Biobank. Using Cox regression, we estimated Hazard ratios (HRs) and 95% confidence intervals (CIs) for early-onset total and breast cancer based on sex-specific composite total cancer polygenic risk scores (PRSs), a breast cancer-specific PRS, and sex-specific health-associated lifestyle scores (HLSs).
Results: In multivariable-adjusted analyses with 2-year latency, higher genetic risk (highest vs lowest tertile of PRS) was associated with significantly increased risks of early-onset total cancer in females (HR, 95% CI: 1.83, 1.49-2.26) and males (2.03, 1.51-2.73) as well as early-onset breast cancer in females (3.06, 2.20-4.26). An unfavorable lifestyle (highest vs lowest category of HLS) was associated with higher risk of total cancer and breast cancer in females across genetic risk categories; the association with total cancer and breast cancer was stronger in the highest genetic risk category than the lowest: HRs (95% CIs) were 1.55 (1.12, 2.14) and 1.69 (1.11, 2.57) in the highest genetic risk category and 1.03 (0.64, 1.67) and 0.81 (0.36, 1.85) in the lowest.
Conclusions: Genetic and lifestyle factors were independently associated with early-onset total and breast cancer risk. Individuals with a high genetic risk may benefit more from adopting a healthy lifestyle in preventing early-onset cancer.
Published by Oxford University Press 2024.